. ♪ (train horn) vo: wherever our trains go, the economy comes to life. norfolk southern. one line, infinite possibilities. >>> a tiny ren waw painting worth a small fortune, but the story of how it was stolen from a baltimore art museum 60 years ago, then bought for $7 at a flea market, the fbi is now on the case. still no idea who stole it or how it wound up in a flea market. and after all that is figured out, there's still yet another question. who owns it? the museum, the woman who bought it $7, or the insurance company? >>> now for another mystery, this one involving one of the most famous paintings in the world. we're talking about leonardo da vinci's mona lisa. a private swiss art foundation says she's not alone. there's another mona lisa out there. and they unveiled it on thursday. so let the debate begin. we brought in john mann, cnn international. his expertise and his piercing eye can help nail it down for us. >> you think that renoir was available? that's jump change to a mona lisa which wasn't the first mona lisa. what they're trying to convince the art world